PCM - Sets up the watchdog timer

[Tibi]

Using the PCM for PIC16F628, how can I increase the time for the watchdog timer, from 2300ms to 10000ms ?
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This message was ported from CCS's old forum
Original Post ID: 13446

[R.J.Hamlett]

:=Using the PCM for PIC16F628, how can I increase the time for the watchdog timer, from 2300ms to 10000ms ?

You can't.
This is a hardware limit, not anything that can be changed by the code. You should not rely even on the 2300mSec, since the time delay varies significantly between chips, and with temperature/voltage etc..
The way to code if you need a long watchdog, is to generate a carefully written 'timer' tick, with an interrupt handler, that decrements a counter, and if the counter is not zero, resets the watchdog. Then in the main code where you would normally do a 'restart_wdt()' call, you instead have a routine to reset the counter, and if this stops happening, when the counter gets to zero, you will get a watchdog. A crude version is below:

//counter for the watchdog
int wtick;

//interrupt routine to handle the 'tick'
#int_timer1
void tick(void) {
//If the wtick value is non zero
if (wtick) {
//decrement wtick
--wtick;
//and reset the hardware watchdog
restart_wdt();
}
}

#define RESET_WDOG() wtick=9

void main() {

setup_counters(RTCC_INTERNAL,WDT_2304MS);
setup_timer_1(T1_INTERNAL|T1_DIV_BY_8);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(FALSE);
setup_vref(FALSE);
enable_interrupts(INT_TIMER1);
enable_interrupts(GLOBAL);
while (true) {
/*As set, the 'tick interrupt' will occur every 104mSec,
with a 20MHz processor clock. Setting wtick to 9, will
result in it taking at least 8 seconds to count down. The
hardware watchdog will occur about 2.3 seconds after
this. Hence so long as the counter is reset at least
once every ten seconds the watchdog should not trigger.
You will have to adjust the value used to suit your
crystal frequency. */
RESET_WDOG();
}
}

This is untested, but should work.

Best Wishes
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This message was ported from CCS's old forum
Original Post ID: 13449

[Tibi]

To R.J.Hamlett

thank you for the answer. I will try to manage the problem in this situation. Any way you sent me good ideas.

Thank you and best regards,

Tibi
___________________________
This message was ported from CCS's old forum
Original Post ID: 13451

[R.J.Hamlett]

:=To R.J.Hamlett
:=
:=thank you for the answer. I will try to manage the problem in this situation. Any way you sent me good ideas.
:=
:=Thank you and best regards,
:=
:=Tibi
Good Luck. :-)
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This message was ported from CCS's old forum
Original Post ID: 13457